1. Field of the Invention
The present invention relates to a swing-arm type optical recording and reproducing apparatus and an optical disk applicable to the same. More particularly, the present invention relates to a swing-arm type optical recording and reproducing apparatus adapted to prevent defocus due to variations in the temperature and wavelength of illuminating light, and an optical disk which is applied to the optical recording and reproducing apparatus so that the swing arm of the optical recording and reproducing apparatus can swing stably.
2. Description of the Related Art
As shown in FIGS. 1 and 2, a conventional swing-arm type optical recording and reproducing apparatus 80 includes a swing arm 2 installed to pivot on a base 1, an actuator 6 for providing a rotational driving force for the swing arm 2, a slider 5 installed at an end portion of the swing arm 2 for scanning a track of an optical disk 20 while floating, due to a dynamic air pressure, on the optical disk 20 supported and rotated by a spindle motor 7, and an optical head installed at the swing arm 2 and the slider 5 in order to optically record/reproduce information.
The optical head includes a light source 11 installed on a mount 3 of the swing arm 2, a beam splitter 12, a photodetector 13, and an objective lens 15 installed at the slider 5. The beam splitter 12 changes the path of incident rays by passing or reflecting the incident rays. That is, the beam splitter 12 passes the rays entering from the light source 11 to direct the rays toward the objective lens 15, and reflects the rays entering from the objective lens 15 to direct the rays toward the photodetector 13. The photodetector 13 detects an information signal recorded on the optical disk 20 and a track error signal.
In the swing-arm type optical recording and reproducing apparatus 80, the swing arm 2 is swung by the driving force of the actuator 6 in a radial direction of the optical disk 20. At this time, a beam L, having passed through the beam splitter 12 after being emitted from the light source 11, is reflected from a reflecting member 14 installed at the end portion of the swing arm 2. A reflected beam M enters and is converged by the objective lens 15 installed at the slider 5, and is focused on a recording surface of the optical disk 20. Subsequently, the beam reflected from the optical disk 20 travels toward the beam splitter 12 via the objective lens 15 and the reflecting member 14, and is reflected toward the photodetector 13 from the beam splitter 12. The photodetector 13 receives incident light, and detects the information signal and the track error signal of the objective lens 15.
In the optical recording and reproducing apparatus 80, the focus position of a beam spot is adjusted by the floatation of the slider 5 due to the dynamic air pressure, thus a separate focusing servomechanism function is not performed. Therefore, in the optical head, there is no focusing servomechanism to correspond to a defocus amount representing a degree of variation in a focus position of a beam spot due to temperature or wavelength variations. Since, in the conventional optical recording and reproducing apparatus 80, a wavelength of the beam varies with temperature variations within about xc2x115 nm, the optical head must be configured so that the defocus amount of the optical head can be sufficiently small with respect to the wavelength variations of about xc2x115 nm for stable recording and reproducing.
Furthermore, the conventional optical disk 20 employed in the above swing-arm type optical recording and reproducing apparatus 80 has a structure shown in FIG. 3. Referring to FIG. 3, an optical disk 20 includes a substrate 21 provided with a spiral groove forming pits 24 on a surface thereof, and a protective layer 23 provided on the substrate 21. In the protective layer 23, recessed grooves 23a face the slider 5 and correspond to the pits 24.
The protective layer 23 has a thickness of about 50 to 100 nm, and a depth of the recessed grooves 23a is about 130 nm. Since the recessed grooves 23a are formed, a floatation height of the slider 5 is about 20 to 100 nm. Thus, there is a problem of unstable movement of the slider 5.
Furthermore, since the light source 11 and the photodetector 13 are installed on the mount 3, the light beam reflected from the optical disk 20 directly passes through air while returning to the photodetector 13 Thus, there is a further problem of significant light loss along the optical path.
Still further, since the focusing servochanism function is not performed, when defocus representing the degree of variation in the focus position due to variations in ambient temperature and variations in the wavelength of the light of the light source occurs, significant errors in the recording/reproducing of information may occur.
Additionally, as a recording density of the optical disk 20 becomes denser, the optical recording and reproducing apparatus 80 requires a mechanism for performing precise servo tracking of the slider 5 so that an optical spot formed on the optical disk 20 can be precisely focused. However, the conventional optical recording and reproducing apparatus 80 performs servo tracking with the actuator 6, which drives the swing arm 2 without a separate actuator for driving the slider 5 independently. Thus, the optical recording and reproducing apparatus 80 is problematic because it is difficult to control the slider 5 precisely.
Accordingly, it is an object of the present invention to provide an optical disk which can be applied to a swing-arm type optical recording and reproducing apparatus adapted to minimizing variations in the floatation height of a slider floated by a dynamic air pressure.
It is another object of the present invention to provide a swing-arm type optical recording and reproducing apparatus having an improved structure capable of restraining the amount of defocus due to variations in ambient temperature and the wavelength of the light of a light source.
Additional objects and advantages of the invention will be set forth in part in the description which follows, and, in part, will be obvious from the description, or may learned by practice of the invention.
The foregoing objects of the present invention are achieved by providing an optical disk applicable to a swing-arm type optical recording and reproducing apparatus, which is rotatably installed on a spindle motor so that information can be recorded on or reproduced from the optical disk by a slider of the optical recording and reproducing apparatus. The slider moves while floating at a predetermined height due to a dynamic air pressure in order to reduce variations in the floating height of the slider. The optical disk includes a substrate having an information recording surface for recording and reproducing an information signal, and a protective layer provided on the information recording surface. The protective layer has a flat even surface that faces the slider.
The above objects of the present invention may also be achieved by providing a swing-arm type optical recording and reproducing apparatus including a swing arm installed in order to be pivoted in a radial direction of an optical disk by a driving source; a suspension with one end fixed to the swing arm for elastically biasing the other end thereof; a slider installed on a surface of the end portion of the suspension facing the optical disk; and an optical head installed at the swing arm and the slider for recording and reproducing information. The optical head restrains defocus due to variations in ambient temperature and variations in the wavelength of the light of a light source, and includes a light source provided at the swing arm for emitting light of a predetermined wavelength; an optical path changing unit provided in the optical path of the light emitted from the light source, changing the proceeding path of incident light; an objective lens installed at the slider, converging the light which is emitted from the light source and enters via the optical path changing unit to form an optical spot on the optical disk; and a photodetector receiving the light which is reflected from the optical disk and enters via the objective lens and the optical path changing unit to detect an information signal and an error signal.